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authorPaolo Bonzini <pbonzini@redhat.com>2012-01-12 10:01:28 -0500
committerLinus Torvalds <torvalds@linux-foundation.org>2012-01-14 18:07:24 -0500
commit0bfc96cb77224736dfa35c3c555d37b3646ef35e (patch)
treeaf5135c929ee8e1bdb38c306b2634dbc547d5189 /block
parent577ebb374c78314ac4617242f509e2f5e7156649 (diff)
block: fail SCSI passthrough ioctls on partition devices
Linux allows executing the SG_IO ioctl on a partition or LVM volume, and will pass the command to the underlying block device. This is well-known, but it is also a large security problem when (via Unix permissions, ACLs, SELinux or a combination thereof) a program or user needs to be granted access only to part of the disk. This patch lets partitions forward a small set of harmless ioctls; others are logged with printk so that we can see which ioctls are actually sent. In my tests only CDROM_GET_CAPABILITY actually occurred. Of course it was being sent to a (partition on a) hard disk, so it would have failed with ENOTTY and the patch isn't changing anything in practice. Still, I'm treating it specially to avoid spamming the logs. In principle, this restriction should include programs running with CAP_SYS_RAWIO. If for example I let a program access /dev/sda2 and /dev/sdb, it still should not be able to read/write outside the boundaries of /dev/sda2 independent of the capabilities. However, for now programs with CAP_SYS_RAWIO will still be allowed to send the ioctls. Their actions will still be logged. This patch does not affect the non-libata IDE driver. That driver however already tests for bd != bd->bd_contains before issuing some ioctl; it could be restricted further to forbid these ioctls even for programs running with CAP_SYS_ADMIN/CAP_SYS_RAWIO. Cc: linux-scsi@vger.kernel.org Cc: Jens Axboe <axboe@kernel.dk> Cc: James Bottomley <JBottomley@parallels.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> [ Make it also print the command name when warning - Linus ] Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'block')
-rw-r--r--block/scsi_ioctl.c45
1 files changed, 45 insertions, 0 deletions
diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
index a2c11f330872..260fa80ef575 100644
--- a/block/scsi_ioctl.c
+++ b/block/scsi_ioctl.c
@@ -24,6 +24,7 @@
24#include <linux/capability.h> 24#include <linux/capability.h>
25#include <linux/completion.h> 25#include <linux/completion.h>
26#include <linux/cdrom.h> 26#include <linux/cdrom.h>
27#include <linux/ratelimit.h>
27#include <linux/slab.h> 28#include <linux/slab.h>
28#include <linux/times.h> 29#include <linux/times.h>
29#include <asm/uaccess.h> 30#include <asm/uaccess.h>
@@ -690,9 +691,53 @@ int scsi_cmd_ioctl(struct request_queue *q, struct gendisk *bd_disk, fmode_t mod
690} 691}
691EXPORT_SYMBOL(scsi_cmd_ioctl); 692EXPORT_SYMBOL(scsi_cmd_ioctl);
692 693
694int scsi_verify_blk_ioctl(struct block_device *bd, unsigned int cmd)
695{
696 if (bd && bd == bd->bd_contains)
697 return 0;
698
699 /* Actually none of these is particularly useful on a partition,
700 * but they are safe.
701 */
702 switch (cmd) {
703 case SCSI_IOCTL_GET_IDLUN:
704 case SCSI_IOCTL_GET_BUS_NUMBER:
705 case SCSI_IOCTL_GET_PCI:
706 case SCSI_IOCTL_PROBE_HOST:
707 case SG_GET_VERSION_NUM:
708 case SG_SET_TIMEOUT:
709 case SG_GET_TIMEOUT:
710 case SG_GET_RESERVED_SIZE:
711 case SG_SET_RESERVED_SIZE:
712 case SG_EMULATED_HOST:
713 return 0;
714 case CDROM_GET_CAPABILITY:
715 /* Keep this until we remove the printk below. udev sends it
716 * and we do not want to spam dmesg about it. CD-ROMs do
717 * not have partitions, so we get here only for disks.
718 */
719 return -ENOIOCTLCMD;
720 default:
721 break;
722 }
723
724 /* In particular, rule out all resets and host-specific ioctls. */
725 printk_ratelimited(KERN_WARNING
726 "%s: sending ioctl %x to a partition!\n", current->comm, cmd);
727
728 return capable(CAP_SYS_RAWIO) ? 0 : -ENOIOCTLCMD;
729}
730EXPORT_SYMBOL(scsi_verify_blk_ioctl);
731
693int scsi_cmd_blk_ioctl(struct block_device *bd, fmode_t mode, 732int scsi_cmd_blk_ioctl(struct block_device *bd, fmode_t mode,
694 unsigned int cmd, void __user *arg) 733 unsigned int cmd, void __user *arg)
695{ 734{
735 int ret;
736
737 ret = scsi_verify_blk_ioctl(bd, cmd);
738 if (ret < 0)
739 return ret;
740
696 return scsi_cmd_ioctl(bd->bd_disk->queue, bd->bd_disk, mode, cmd, arg); 741 return scsi_cmd_ioctl(bd->bd_disk->queue, bd->bd_disk, mode, cmd, arg);
697} 742}
698EXPORT_SYMBOL(scsi_cmd_blk_ioctl); 743EXPORT_SYMBOL(scsi_cmd_blk_ioctl);